I can´t make a cut between this two sketches, sketch 8 and sketch 10 can anyone help me understand my error?
The basic answer is that you usually need to have the same number of control points in each sketch when doing a loft. When you use a circle, this is usually not a rule you need to follow, but it is in this case. I think you could solve the problem in other ways like using guide curves, or even a center-line, but these two methods should work as well. Give them a try.
My SolidWorks models are 2016, so you won't be able to open them. The Step files should work.
Answered with a tutorial: https://grabcad.com/tutorials/loft-cut